This outbreak investigation is over. Illnesses could continue because people may not know they could get a Salmonella infection from contact with dairy calves or other cattle. Information about how to prevent illness when handling calves and cattle is available for Livestock Handlers.

This outbreak investigation is over. Illnesses could continue because people may not know they could get a Salmonella infection from contact with dairy calves or other cattle.

CDC, several states, and the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (USDA-APHIS) investigated a multistate outbreak of multidrug-resistant Salmonella Heidelberg infections. Epidemiologic and laboratory evidence indicated that contact with dairy calves and other cattle was the likely source of this outbreak.

A total of 56 people infected with the outbreak strains of Salmonella Heidelberg were reported from 15 states. Illnesses started on dates ranging from January 27, 2015 to November 25, 2017. Of those with available information:

35% of people were hospitalized. No deaths were reported.

35% of people in this outbreak are children younger than 5 years.

Epidemiologic, laboratory, and traceback investigations linked ill people in this outbreak to contact with calves, including dairy calves.

In interviews, ill people answered questions about contact with animals and foods eaten in the week before becoming ill. Of the 54 people interviewed, 34 (63%) reported contact with dairy calves or other cattle. Some of the ill people interviewed reported that they became sick after their calves became sick or died.

Surveillance in veterinary diagnostic laboratories showed that calves in several states were infected with the outbreak strains of multidrug-resistant Salmonella Heidelberg

Information collected earlier in the outbreak indicated that most of the calves came from Wisconsin. Regulatory officials in several states attempted to trace the origin of calves linked to more recent illnesses. A specific source of cattle linked to newer illnesses was not identified.

Antibiotic resistance testing conducted by CDC on clinical isolates from ill people shows that the isolates were resistant to multiple antibiotics.

Antibiotic resistance may be associated with increased risk of hospitalization, development of a bloodstream infection, or treatment failure in patients.

These findings match results from standard antibiotic resistance testing methods used by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory on 10 isolates from 9 ill people and 1 animal. All 10 isolates were resistant to amoxicillin-clavulanic acid, ampicillin, cefoxitin, ceftriaxone, streptomycin, sulfisoxazole, and tetracycline. In addition, nine had reduced susceptibility to ciprofloxacin, nine were resistant to trimethoprim-sulfamethoxazole, six were resistant to nalidixic acid, four were resistant to chloramphenicol, and one was resistant to gentamicin. All 10 isolates tested were susceptible to azithromycin and meropenem.

Follow these steps to prevent illness when working with any livestock:

Always wash your hands thoroughly with soap and water right after touching livestock, equipment, or anything in the area where animals live and roam. Use dedicated clothes, shoes, and work gloves when working with livestock. Keep and store these items outside of your home.

It is especially important to follow these steps if there are children younger than 5 years in your household. Young children are more likely to get a Salmonella infection because their immune systems are still developing.

Work with your veterinarian to keep your animals healthy and prevent diseases.

It is important to remember that cattle can carry Salmonella and not appear sick. However, in this outbreak, some people did notice illness in their cattle, especially among calves. Livestock handlers should watch for sicknesses in dairy calves and consult their veterinarian if needed.

Previous Outbreak Advisories

Since the last update on August 2, 2017, eight more ill people have been reported from six states.

CDC, several states, and the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (USDA-APHIS) are investigating a multistate outbreak of multidrug-resistant Salmonella Heidelberg infections.

A total of 54 people infected with the outbreak strains of Salmonella Heidelberg have been reported from 15 states.

Seventeen (35%) people have been hospitalized. No deaths have been reported.

Illnesses started on dates ranging from January 27, 2015 to October 15, 2017.

Eighteen (33%) people in this outbreak are children under the age of 5.

Epidemiologic and laboratory investigations linked ill people in this outbreak to contact with calves, including dairy calves.

In interviews, ill people answered questions about contact with animals and foods eaten in the week before becoming ill. Of the 54 people interviewed, 34 (63%) reported contact with dairy calves or other cattle. Some of the ill people interviewed reported that they became sick after their dairy calves became sick or died.

Ongoing surveillance in veterinary diagnostic laboratories showed that calves in several states continue to get sick with the outbreak strains of multidrug resistant Salmonella Heidelberg. ‎

Information collected earlier in the outbreak indicated that most of the calves came from Wisconsin. Regulatory officials in several states are now tracing the origin of the calves that are linked to the newer illnesses.

Antibiotic resistance testing conducted by CDC on clinical isolates from ill people shows that the isolates were resistant to multiple types of antibiotics.

Antibiotic resistance may be associated with increased risk of hospitalization, development of a bloodstream infection, or treatment failure in patients.

All eight isolates from ill people were resistant to amoxicillin-clavulanic acid, ampicillin, cefoxitin, ceftriaxone, streptomycin, sulfisoxazole, and tetracycline, and had reduced susceptibility to ciprofloxacin. Seven isolates were also resistant to trimethoprim-sulfamethoxazole. Five were also resistant to nalidixic acid. Three were also resistant to chloramphenicol. All eight isolates tested were susceptible to azithromycin and meropenem.

Follow these steps to prevent illness when working with any livestock:

Always wash your hands thoroughly with soap and water right after touching livestock, equipment, or anything in the area where animals live and roam. Use dedicated clothes, shoes, and work gloves when working with livestock. Keep and store these items outside of your home.

It is especially important to follow these steps if there are children under age 5 in your household. Young children are more likely to get a Salmonella infection because their immune systems are still developing.

Work with your veterinarian to keep your animals healthy and prevent diseases.

This investigation is ongoing and we will provide updates as more information becomes available. Livestock owners should continue to watch for increased sicknesses in dairy calves and consult their veterinarian if needed.

CDC, several states, and the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (USDA-APHIS) are reopening the investigation of a multistate outbreak of multidrug-resistant Salmonella Heidelberg infections.

Ten more people infected with the outbreak strains of Salmonella Heidelberg have been reported since March 20, 2017, when CDC closed the outbreak investigation.

Whole genome sequencing on clinical samples from ill people showed a close genetic relationship between the bacteria that sickened people after March 20, 2017, and the bacteria that sickened people before that time. This means that people in both groups were more likely to share a common source of infection and that this outbreak is ongoing.

A total of 46 people infected with the outbreak strains of Salmonella Heidelberg have been reported from 14 states.

14 (30%) people have been hospitalized. No deaths have been reported.

Illnesses started on dates ranging from January 27, 2015 to July 11, 2017.

15 (33%) people in this outbreak are children under the age of 5.

Epidemiologic and laboratory investigations linked ill people in this outbreak to contact with calves, including dairy bull calves. Dairy bull calves are young, male cattle that may be raised for meat.

In interviews, ill people answered questions about contact with animals and foods eaten in the week before becoming ill. Of the 44 people interviewed, 29 (66%) reported contact with dairy bull calves or other cattle. Some of the ill people interviewed reported that they became sick after their dairy bull calves became sick or died.

Ongoing surveillance in veterinary diagnostic laboratories showed that calves in several states continued to get sick with the outbreak strain of multidrug resistant Salmonella Heidelberg after reports of illnesses in people had stopped. ‎

Information collected earlier in the outbreak indicated that most of the calves came from Wisconsin. Regulatory officials in several states are now tracing the origin of the calves that are linked to the newer illnesses.

Antibiotic-resistance testing conducted by CDC on clinical isolates from ill people shows that the isolates were resistant to multiple types of antibiotics.

Antibiotic resistance may be associated with increased risk of hospitalization, development of a bloodstream infection, or treatment failure in patients.

The eight isolates tested were susceptible to gentamicin, azithromycin, and meropenem. All eight were resistant to amoxicillin-clavulanic acid, ampicillin, cefoxitin, ceftriaxone, streptomycin, sulfisoxazole, and tetracycline, and had reduced susceptibility to ciprofloxacin. Seven isolates were also resistant to trimethoprim-sulfamethoxazole. Five were also resistant to nalidixic acid. Three were also resistant to chloramphenicol.

Follow these steps to prevent illness when working with any livestock:

Always wash your hands thoroughly with soap and water right after touching livestock, equipment, or anything in the area where animals live and roam. Use dedicated clothes, shoes, and work gloves when working with livestock. Keep and store these items outside of your home.

It is especially important to follow these steps if there are children under age 5 in your household. Young children are more likely to get a Salmonella infection because their immune systems are still developing.

Work with your veterinarian to keep your animals healthy and prevent diseases.

This investigation is ongoing and we will provide updates as more information becomes available. Livestock owners should continue to watch for increased sicknesses in dairy calves and consult their veterinarian if needed.

March 20, 2017

CDC worked with the Wisconsin Department of Health Services; Wisconsin Department of Agriculture, Trade and Consumer Protection; Wisconsin Veterinary Diagnostic Laboratory; Wisconsin State Laboratory of Hygiene; several other states; and the U.S. Department of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS) to investigate a multistate outbreak of multidrug-resistant Salmonella Heidelberg infections.

Public health investigators used the PulseNet system to identify illnesses that were part of this outbreak. Thirty-six people infected with the outbreak strains of Salmonella Heidelberg were reported from ten states. A list of states and the number of cases in each can be found on the Case Count Map page.

Among 36 people with available information, illnesses started on dates ranging from January 27, 2015 to January 16, 2017. After the initial announcement on November 28, 2016, investigators identified seven people in four states who were infected with the outbreak strains in 2015. Based on interviews with the ill people and whole genome sequencing (WGS) data, these people were added to the total case count for the outbreak.

Ill people ranged in age from less than 1 year to 72, with a median age of 18. Of ill people, 60% were female. Among 31 ill people with available information, 13 (42%) were hospitalized, and no deaths were reported.

WGS showed that isolates from ill people were closely related genetically to one another. This close genetic relationship means that people in this outbreak were more likely to share a common source of infection.

Investigation of the Outbreak

Epidemiologic, traceback, and laboratory investigations identified sick calves, including dairy bull calves from livestock markets in Wisconsin, as the likely source of most of these infections. Dairy bull calves are young, male cattle that have not been castrated and may be raised for meat. Some calves in this outbreak were also purchased for use with 4-H projects.

In interviews, ill people answered questions about any contact with animals and foods eaten in the week before becoming ill. Of the 36 people interviewed, 25 (69%) reported contact with dairy bull calves or other cattle. Some of the ill people interviewed reported that they became sick after their dairy bull calves became sick or died.

One ill person’s dairy calves were tested for the presence of Salmonella bacteria. This laboratory testing identified Salmonella Heidelberg. Additionally, environmental samples were collected from a livestock market in Wisconsin, and these samples also identified Salmonella Heidelberg. Further testing using WGS showed that isolates from ill people were closely related genetically to both the isolates from these calves and to the livestock market. This close genetic relationship means that the human infections in this outbreak were likely linked to sick calves.

As part of routine surveillance, the Wisconsin State Laboratory of Hygiene, one of seven regional labs affiliated with CDC’s Antibiotic Resistance Laboratory Network, conducted antibiotic resistance testing on clinical isolates from the ill people associated with this outbreak. These isolates were found to be resistant to multiple antibiotics and shared the same DNA fingerprints, showing the isolates were likely related to one another.

WGS identified multiple antimicrobial resistance genes in outbreak-associated isolates from 26 ill people, 43 cattle, and 10 from animal environments. Resistance genes correlated with results from standard antibiotic resistance testing methods used by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory on clinical isolates from five ill people in this outbreak. All five isolates tested were resistant to amoxicillin-clavulanic acid, ampicillin, cefoxitin, ceftriaxone, streptomycin, sulfisoxazole, and tetracycline, had reduced susceptibility to ciprofloxacin, and were susceptible to azithromycin, gentamicin, and meropenem. Four of the five isolates were also resistant to trimethoprim-sulfamethoxazole, and two of these were resistant to chloramphenicol and nalidixic acid. Antibiotic resistance limits treatment options and has been associated with increased risk of hospitalization, bloodstream infections, and treatment failures in patients.

Traceback information collected during the outbreak indicated that most of the calves originated in Wisconsin. Multiple farms and animal markets in Wisconsin were identified during the investigation, including one market where environmental samples were collected and demonstrated presence of the outbreak strain of Salmonella Heidelberg. Wisconsin health and agriculture officials continue to work with other states to identify other herds that may be affected. They also are identifying ways to work with farms and livestock markets to reduce the risk of Salmonella contamination and infection in dairy calves.

This outbreak investigation is over. However, infections in calves continue to be reported and people can still get a Salmonella infection from contact with these livestock. Read more information about Salmonella and livestock and how people can reduce the chance they will get an infection. Livestock owners should continue to monitor for increased morbidity and mortality in dairy calves and consult their veterinarian if noted.

November 28, 2016

CDC is working with Wisconsin health, agriculture, and laboratory agencies, several other states, and the U.S. Department of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS) to investigate a multistate outbreak of multidrug-resistant Salmonella Heidelberg infections.

Public health investigators used the PulseNet system to identify illnesses that may have been part of this outbreak. PulseNet, coordinated by CDC, is the national subtyping network of public health and food regulatory agency laboratories. PulseNet performs DNA fingerprinting on Salmonella bacteria isolated from ill people by using techniques called pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS). CDC PulseNet manages a national database of these DNA fingerprints to identify possible outbreaks.

Twenty-one people infected with an outbreak strain of Salmonella Heidelberg have been reported from eight states. A list of states and the number of cases in each can be found on the Case Count Map page.

Among 19 people with available information, illnesses started on dates ranging from January 11, 2016 to October 24, 2016. Ill people range in age from less than 1 year to 72, with a median age of 21. Sixty-two percent of ill people are female. Among 19 ill people with available information, 8 (42%) reported being hospitalized, and no deaths have been reported.

WGS showed that isolates from ill people are closely related genetically to one another. This close genetic relationship means that people in this outbreak are more likely to share a common source of infection.

This outbreak can be illustrated with a chart showing the number of people who became ill each day. This chart is called an epidemic curve or epi curve. Illnesses that occurred after October 24, 2016 might not be reported yet because reporting takes an average of 2 to 4 weeks. Please see the Timeline for Reporting Cases of Salmonella Infection for more details.

Investigation of the Outbreak

Epidemiologic, traceback, and laboratory findings have identified dairy bull calves from livestock markets in Wisconsin as the likely source of infections. Dairy bull calves are young, male cattle that have not been castrated and may be raised for meat. Dairy bull calves in this outbreak have also been purchased for use with 4-H projects.

In interviews, ill people answered questions about any contact with animals and foods eaten in the week before becoming ill. Of the 19 people interviewed, 15 (79%) reported contact with dairy bull calves or other cattle. Some of the ill people interviewed reported that they became sick after their dairy bull calves became ill or died.

One ill person’s dairy calves were tested for the presence of Salmonella bacteria. This laboratory testing identified Salmonella Heidelberg in the calves. Further testing using WGS showed that isolates from ill people are closely related genetically to isolates from these calves. This close genetic relationship means that the human infections in this outbreak are likely linked to ill calves.

As part of routine surveillance, the Wisconsin State Laboratory of Hygiene, one of seven regional labs affiliated with CDC’s Antibiotic Resistance Laboratory Network, conducted antibiotic resistance testing on clinical isolates from the ill people associated with this outbreak. These isolates were found to be resistant to antibiotics and shared the same DNA fingerprints, showing the isolates were likely related to one another.

WGS identified multiple antimicrobial resistance genes in outbreak-associated isolates from fifteen ill people and eight cattle. This correlated with results from standard antibiotic resistance testingExternal methods used by CDC’s National Antimicrobial Resistance Monitoring System (NARMS)External laboratory on clinical isolates from two ill people in this outbreak. The two isolates tested were susceptible to gentamicin, azithromycin, and meropenem. Both were resistant to amoxicillin-clavulanic acid, ampicillin, cefoxitin, ceftriaxone, chloramphenicol, nalidixic acid, streptomycin, sulfisoxazole, tetracycline, and trimethoprim-sulfamethoxazole and had reduced susceptibility to ciprofloxacin. Antibiotic resistance limits treatment options and has been associated with increased risk of hospitalization, bloodstream infections, and treatment failures in patients.

Traceback information available at this time indicates that most calves in this outbreak originated in Wisconsin. Wisconsin health and agriculture officials continue to work with other states to identify herds that may be affected.

This investigation is ongoing. CDC will provide updates when more information is available.

Advice and Information

Advice for Livestock Handlers

This outbreak is a reminder to use a One Health approach to preventing illness, which recognizes that the health of people is connected to the health of animals and the environment. Follow these steps prevent illness when handling any livestock, like dairy calves:

Always wash hands thoroughly with soap and water right after touching livestock, equipment for animals, or anything in the area where animals live and roam.

This is especially important to do before preparing or consuming food or drink for yourself or others.

Adults should supervise hand washing for young children.

Use hand sanitizer if soap and water are not available right away.

Use dedicated shoes, work gloves, and clothing that you only use when working with livestock. Keep these items outside of your home.

Do not eat or drink in the areas where livestock live and roam.

Do not allow toys, pacifiers, spill-proof cups, baby bottles, strollers, or similar items in livestock areas.

Wash hands after removing any clothes and shoes you wore while working with livestock.

Work with your veterinarian to keep your livestock healthy.

If you think your livestock are sick, talk to your veterinarian as soon as possible and take extra care to wash your hands after working with the animals and use separate clothes when caring for them.

Children, adults over age 65, and people with compromised immune systems should limit their contact with sick animals.

Advice for Veterinarians

If veterinarians recognize ill dairy calves with laboratory-confirmed Salmonella Heidelberg, they should report the illness to their State Animal Health Official.

Laboratory testing, to include antimicrobial susceptibility testing, is recommended among dairy calves diagnosed with Salmonella Heidelberg, especially those associated with human illness.

If you suspect that a calf has a Salmonella infection, collect a fecal sample and submit it to a state or university veterinary diagnostic laboratory for culturing and pulsed-field gel electrophoresis (PFGE) testing.

For testing, the American Association of Veterinary Laboratory Diagnosticians (AAVLD) recommends submitting fecal samples to a state or university veterinary diagnostic laboratory for Salmonella culturing and PFGE.

If the laboratory isolates Salmonella but cannot perform PFGE, the isolate may be forwarded to a laboratory that can perform the procedure. This may be one of the AAVLD labs in your area. To locate an AAVLD laboratory in your area, go to AAVLD Accredited LabsExternal, or go to the AAVLD’s home pageExternal and click on the “Accreditation” link on the top menu bar.

Talk to your clients about reducing the risk of transmission of Salmonella illness from cattle to their family.

Be sure to tell clients that Salmonella infections are a zoonotic disease, meaning that the infection can spread between animals and people. If the client or any of their family members are ill, encourage them to contact a health care provider immediately.

Information for Health Care Providers

Salmonella bacteria live in the intestinal tracts of animals, including cattle. Cattle may become ill from Salmonella, but usually have no signs of illness. Young calves are more susceptible to being ill. The primary mode of transmission to humans is fecal-oral and is associated with contact with animals or their environments.

Clinicians should consider multidrug-resistant (MDR) Salmonella Heidelberg infection in the differential diagnosis of patients with exposure to cattle, farms, or farm workers and symptoms compatible with salmonellosis (e.g., diarrhea, fever, and abdominal cramps).

Guidance for clinicians whose patients have suspected or confirmed Salmonella Heidelberg infection related to this outbreak:

Testing

Obtain a culture (stool or blood, as indicated by symptoms and signs).

Request antimicrobial susceptibility testing.

Treatment

Most patients with nontyphoidal Salmonella do not require antibiotic treatment (exceptions may include patients <6 months, >50 years, and those who are immunocompromised or severely ill; please refer to treatment guidelinesExternal for additional information).

If treatment is indicated and MDR Salmonella Heidelberg infection is suspected, clinicians should begin treatment with azithromycin until susceptibility results of the patient’s isolate are available.

Follow up

Obtain follow-up stool cultures for patients who have culture-confirmed MDR Salmonella Heidelberg and who are: